In a commercial establishment such as a retail store, a queue (line) of customers may be formed at the checkout counter when the number of customers who want to pay for their purchases increases to a certain point, and this necessitates the customers to wait in the queue for their turn. If the wait time of the customers in the queue, i.e., the period of time from when each customer joins the queue until when checkout is completed, can be grasped, it is possible to develop measures for improving the operation of the store based on the wait time, to thereby improve the customer satisfaction and streamline the operation of the commercial establishment.
To obtain the wait time of the customers, it may be conceived to capture a video image with a camera to cover the place where a queue of customers may be formed, set a measurement area so as to correspond to a region in the captured image where a queue of customers may be formed, and measure a stay duration of each customer in the measurement area, namely, a period of time from when each customer enters the measurement area to when the customer exits the measurement area. As a technology relating to such measurement of stay duration, it is known to analyze the information of multiple image frames comprehensively to track the movement path of each customer, namely, to obtain a movement line (movement trajectory) representing the path taken by each customer, and based on the movement line, calculate the stay duration of each customer in an area of interest (see JP2004-348618A).
In a state where a queue of multiple persons is formed, some of the persons may overlap each other along the line of sight of the camera so that a “background” person may be blocked from view. This phenomenon is known as occlusion. If occlusions occur, the accuracy of person detection decreases and the movement lines in the measurement area may become incomplete. Namely, the movement lines may include a missing part in the measurement area. In such a case, if stay durations are measured based on the movement lines, accurate stay durations may not be obtained. The aforementioned conventional technology takes no measure to address this problem.
It may be conceived to remove a movement line from measurement if the movement line is incomplete in the measurement area. In this way, it is possible to avoid assessing the staying state (queue property) based on inaccurate stay durations. However, the assessment of the staying state is important particularly when the store is crowded with customers, and under such crowded condition, occlusion of one customer by another tends to occur frequently and a larger number of movement lines tend to become incomplete in the measurement area. Therefore, if movement lines are removed from measurement for the reason that they are incomplete in the measurement area, it is not possible to accurately grasp the staying state under crowded condition. Thus, it is desired to provide an appropriate compensation process which makes it possible to obtain, even for a person (customer) whose movement line in the measurement area is incomplete, a stay duration comparable to that which would be obtained if the movement line in the measurement area were complete.
The present invention is made to solve the aforementioned problems in the prior art, and a primary object of the present invention is to provide a stay duration measurement device, a stay duration measurement system and a stay duration measurement method configured to be able to obtain, even for a moving object whose movement line in a measurement area is incomplete, a stay duration comparable to that which would be obtained if the movement line in the measurement area were complete.